The present invention relates to a machine which is intended for joining together mutually crossing rods with the aid of wire-ties, and particularly for lashing or tying reinforcement rods, said machine including a wire guide device having a curved guide surface and being positioned so that the guide surface will substantially surround an intersection point of two rods on three sides thereof, means for feeding at least one wire to said device so that the wire is bent by said guide surface in a manner to form a wire-stirrup which embraces said intersection point on three sides thereof, and a rotatable twisting head by means of which the free legs of the wire-stirrup are twisted around each other on the fourth side of the rod intersection point.
The reinforcement rods or irons of tied mesh reinforcements are traditionally tied or lashed with the aid of simple, manually operated tools, and the task of tying the irons is therefore highly time-consuming, costly and laborious, and is liable to cause strain injuries to the workman involved, among other things. Such strain, or wear on the joints, is caused by the fact that when tying together the reinforcement irons of concrete slab reinforcements, floor structures or the like with the aid of present-day tools, it is necessary for the workman to remain stooped over long periods of time, therewith subjecting the spine to undue loads.
The reinforcement irons are normally tied together with the aid of pliers or "twisters" by means of which the ends of a wire-tie or stirrup positioned manually around the reinforcement rods at the various intersection points are intertwined to provide a firm and durable connection. Conventional tying of reinforcement rods is also encumbered with accident risks, particularly when working on roofs, bridges and the like, due to the stooped position in which the workman is forced to work, therewith placing the workman in danger of falling.
The present invention is based on the realization that the work of tying reinforcement rods can be made much more effective while eliminating, or substantially reducing the risk of injury, when tying can be effected with the aid of a tying machine which enables the workman to work in an upright position.
An automatic tying machine is known from DE-A1-1434519. This machine, however, is a hand-operated machine which requires the workman to stoop when tying the reinforcement bars of floor reinforcements and the like. Furthermore, the machine can only work with pre-bent wire-stirrups of standard sizes. The tying head used with this machine is also relatively complicated, and includes two parts which can be moved axially in relation to one another and which are intended to hold the legs of a wire-stirrup between said parts. This mechanism is highly susceptible to damage and to the presence of contaminants, because of the small tolerances and clearances involved, and is hardly suited for use on building sites.
WO-88/01671 describes a tying machine which enables tying to be effected in an upstanding position. The function of this machine also depends on the use of prefabricated standard-size wire-stirrups housed in a magazine.
In many instances, particularly within the building industries of different countries, tying is effected with the aid of relatively thin wire-ties which are bent to an appropriate stirrup-like shape by the workman on the working site, prior to placing the ties or stirrups over the point of intersection of, for instance, two reinforcement rods or bars.
There is at present no suitable machine which will facilitate this type of tying, in which pre-cut wire lengths are not formed into stirrup-like ties until the actual tying operation is commenced.
In an attempt to automatize tying operations with the use of relatively thin wires, there have earlier been proposed tying machines which include a spool from which wire is continuously taken and passed around the rods in conjunction with a tying operation. These machines have not been found successful in practice, probably due to their unrealibility in operation, among other things. When using such machines, it is also difficult to pass the end of the wire around the rods, in an open groove and up into a twisting head. Because of this, telescopically displaceable devices (see GB-A-2171038 and DE-A1-2223099) have been used, although these devices require a relatively large amount of free space beneath the rods that are to be tied together. These devices must also be provided with wire feed means and wire cutting means, which makes it difficult to run the machine on battery power, owing to the high energy consumption of such means. The machine described in the German patent specification also includes a wire aligning mechanism. The provision of such a mechanism is necessary owing to bending of the wire as it is taken from a spool, therewith complicating guiding of the wire. The use of a wire aligning mechanism also increases energy consumption and adds to the weight of the machine.
DE-B1-1138207 describes a machine which includes a hook-shaped device which requires a relatively large space on the underside of the rods to be tied together.
U.S. Pat. No. 3,368,590 describes a machine which, in order to ensure that the end of the wire is inserted into the twisting head, includes a chain mechanism which draws the end of the wire completely around the rods. This machine is relatively complicated and heavy and consumes a large amount of energy. CH-A-408384 teaches a machine in which the end of a wire is bent into the twisting head by means of a liftable plate. This machine is also relatively complicated, heavy and energy demanding.